Many people associate crayfish with their youth. Mention the word
“crayfish” and people respond with something like “oh ya, I used to
catch them down at the creek when I was a kid”.

However the hobby of keeping crayfish in captivity has been rampantly
growing in popularity among people of all ages. Being able to observe
them in an aquarium fosters appreciation beyond the simple childhood
curiosity. This is especially true in Japan and some European countries
where they have been quite en vogue for decades. The United
States usually plays catch-up with aquarium trends, and is following
suit with its own crayfish craze. Crayfish are becoming more commonly
seen for sale in aquarium stores and in Internet auctions and websites.

This gain in popularity comes at no surprise to the people that are
familiar with crays. Once exposed to their interesting behaviors,
individual personalities and attractive colors and patterns people often
develop the extreme fascination that borders on obsession, similar to
many other aquarium genres. I thought I would take a moment to
write an article that covers the very basics of keeping crayfish. This
should give all those people interested in becoming involved with
crayfish a foundation on what it takes to do so.
Hopefully you will see that they are very easy to care for, which is one
of the endearing qualities making them so popular.

Housing

Crayfish are among the least demanding animals kept as pets, making them
suitable for both children and adults. Compared to other aquatic and
semi-aquatic animals, they only require the simplest living conditions,
with filters and air pumps being optional extras rather than essential
pieces of kit. That said, most people keep crayfish in a typical
aquarium-type set up that includes a filter, and if you choose to keep
your crayfish this way, so much the better. But at the bare minimum all
you need for a crayfish enclosure is a small body of fresh water deep
enough to cover the animal completely, and a rock or branch that allows
it to climb out of the water (without being able to escape, of course!).
Note that being able to climb out of the water is an essential
requirement if the water is not aerated or filtered; crayfish need lots
of oxygen, and in still water conditions, such as in a tank without a
filter or airstone, they will get the oxygen they need from the air. But
if they can’t climb out of the water easily, they will effectively
drown.

Crayfish do not need to be kept a true aquarium, although this provides
the best viewing of these creatures. The container can be as simple as a
5-gallon bucket or a plastic shoebox. Just make sure that the rim of
whatever container you use is taller than the crayfish is long: they are
amazing escape artists! If the container is not tall enough, they will
probably need a vented lid to keep them contained. Crayfish are capable
of climbing air hoses or anything else that extends high enough for them
to reach the top.

Most crayfish burrow to some extent, whether a full-blown tunnel with
complex chambers dug into the mud or simply a depression excavated
underneath a submerged rock or branch. In captivity they will feel much
more secure if given some type of cave within which they can reside. PVC
tubes at least partially buried in the gravel are particularly welcomed
by those crayfish species that build extensive burrows in the wild.
Otherwise ceramic or plastic pipes cut in half lengthwise and placed on
top of the substrate can be used for form shelters appreciated by most
crayfish. Alternatively you can allow the crayfish to dig its own home
by resting a large flat rock (like a slate) on top of several inches of
gravel.

Having plenty of hiding places is especially important when attempting
to keep more than one crayfish in a container. Some species are are
fairly tolerant of one another provided they are not overcrowded, but
others are very territorial and aggressive. Even the ones that are not
aggressive toward each other most of the time may decide to attack and
consume a tank mate who has recently molted. During the molting process
the crayfish is weak and the body is soft and vulnerable, making it an
easy meal for a hungry tankmate. Providing plenty of hiding places gives
the molting crayfish a chance to escape attack during this dangerous
time.

Ideally, you should remove a crayfish from its tank mates before the
molting process begins and only replace it after the exoskeleton
(‘shell’) has completely hardened and it is active and feeding normally.
How will you know when a crayfish is getting ready to molt? Crayfish,
like most other crustaceans, stop feeding shortly (usually at least a
day or more) before shedding the old skeleton. If you notice that a
crayfish in your collection is not eating, that could mean that it is
about to molt and if maintained in a multi-specimen aquarium now would
be a good time to isolate it from its tankmates. Of course loss of
appetite can indicate other problems as well, so you should also check
water quality and chemistry parameters and look for any signs of disease
or physical damage.

Water Quality

If no filtration is used, the water will have to be completely changed
on a regular basis, at least once per week. If gravel is used in the
tank it should be vacuumed or rinsed to remove excess detritus.
Otherwise a bare bottom is fine to use and easy to keep clean. Ornaments
and the sides of the tank should be left untouched to leave sufficient
beneficial bacteria to keep the water adequately clean. If you detect
ammonia or nitrite in the water at any time that means that there aren’t
enough bacteria in the tank as it is, and adding a filter will be
useful.
Undergravel filters are not the best choice for crayfish since these
burrowing animals will move the gravel about creating exposed areas of
the filter plate dramatically reduces the efficiency of this type of
filter. Internal or external canister filters as well as
hang-on-the-back filters that provide for biological filtration are a
much better choice. Air-powered sponge filters also work great but I
have found that some species like to chew on them. This never seemed to
harm the crayfish, but the filter will have to be replaced after they
have shaved it down sufficiently. The possibility of their digestive
tract becoming impacted from the indigestible sponge material should not
be completely ignored, but I have never seen any evidence of this
hypothetical problem.

[Editor’s note: like Justin, I’ve also noticed that large
crustaceans such as crabs enjoy picking away at sponges. Most likely
they consume the organic matter trapped in the sponge and discard the
actual sponge material itself. Even if they do eat some of the sponge, I
agree with Justin that this doesn’t seem to cause them any harm.]

Temperature

Crayfish come from both temperate and tropical zones, and water
temperature will depend upon which species you are keeping. A heater is
not required and should not be used in tanks holding most of the North
American species, though species from the southern United States can
tolerate temperatures as high as 82 degrees F (28 degrees C) without
problems. Two very popular North American species are Procambarus
alleni and Procambarus clarkii, both of which are species
from the southern US. Colorful varieties are grown in large numbers in
ponds specifically for the aquarium industry.

But other North American species are showing up in the trade, albeit on
a much smaller scale, and in the case of these less frequently seen
crayfish you should make sure you know where they come from so that you
can maintain them at an appropriate temperature. As a general rule
though, erring on the side of keeping North American species too cool is
better than keeping them too warm, and most do well left at room
temperature.

Australian species are increasingly popular, and most of those require
tropical temperatures around 77 degrees F (25 degrees C).

[Editor’s note: In the United Kingdom, it is illegal to keep
coldwater crayfish in home aquaria without a specific license. This is
because at least one North American species has become widely
established in British rivers, and by spreading a crayfish plague has
lead to the virtual extinction of the native crayfish. Any crayfish
legally sold in a British tropical fish shop will be tropical species
from Australia, and consequently must be kept in a heated aquarium.]

Feeding

Crayfish are omnivorous scavengers, feeding primarily on plants, algae
and organic detritus. Crayfish do not often find sources of animal
protein such as a dead fish, and such meals are very precious to them,
aggressively defending such a meal against other scavengers.
But will crayfish actually kill and eat your fish? In an aquarium it is
uncommon for crayfish to catch and eat healthy fish, though the odds on
such an event depend on the size of aquarium, the number of fish in the
aquarium, what species of crayfish is being kept, and even whether the
crayfish is well fed or not. So while it is unlikely that a crayfish
will catch your fish, there is a possibility, particularly where small
or slow moving fish are concerned. Most of the time crayfish are seen
eating a fish that fish was already dead or dying, and the crayfish was
simply doing its natural duty of being a scavenger. Without knowing
this, the aquarist might falsely accuse the crayfish of murder when he
notices the crayfish chewing on the carcass!

Crayfish need to be fed a small amount of food every other day or so.
Any excess food should be immediately removed. Foods to feed your
crayfish include leafy green vegetables such as Romaine lettuce (or
other varieties); dried seaweed like Nori; sinking pellet foods such as
shrimp or algae pellets; flake food; and freeze dried or frozen foods
such as fish, krill, tubifex worms, bloodworms, squid, clam, etc. Since
animal protein is rarely encountered in the wild, it is best to feed
crayfish mostly plant or algae based foods, and only supplement with
animal flesh. However, some aquarists feed strictly shrimp pellets with
no apparent problems.

If a crayfish remains soft for an extended period of time, i.e., for
more than one day after molting, this can mean that it is not receiving
enough calcium in its diet or that the pH or hardness of the water is
too low. Transferring the soft specimen to water with high hardness can
help if this is the problem, but it is best to avoid this problem by
keeping crayfish in hard water and feeding them foods rich in calcium.
There are some brands of foods specifically formulated for crustaceans
that have a higher level of calcium added, such as JBL NovoCrabs Food
Chips and Sera Crabs Natural Complete Diet. Calcium can also be added to
other foods by dabbing moist food with a small amount of calcium
carbonate powder before feeding your cray.

Crayfish sometimes die during the moulting process, a problem apparently
caused by an iodine deficiency. Iodine, in the form of potassium iodide,
can be added to the water on a weekly basis to alleviate problems with
the molting process. Iodine drops sold for use in marine tanks work well
for this, though a half dose rather than full dosage is all that is
required. Foods that contain the algae Spirulina sp. or
Chlorella sp. are naturally high in iodine and can be helpful as
well.

Disease

It is a very bad idea to mix together crayfish from different
continents. While there is a risk of spreading disease when crayfish are
placed in the same tank as another one, one disease in particular poses
a very great threat. Known as the Crayfish Plague it is carried by North
American crayfish species. It is a fungus, Aphanomyces astaci,
and American crayfish have apparently evolved to tolerate the fungus
without much problem. However, it is lethal to many other types of
crayfish, including those from Australia and Eurasia.

Never place any crayfish native to another continent together with those
from North America. In addition, be very careful not to share any
equipment such as nets or buckets when working with North American and
non-North American species. The same precautions hold for gravel, pipes
and other decorations.

Another disease that can threaten crayfish is White Spot Disease. This
is primarily a disease that effects shrimps, but may be transmittable to
crayfish if they are fed with raw food made from infected shrimp. Be
sure that any food containing shrimp has been cooked in order to destroy
the virus.

If you intend to keep multiple crayfish specimens in a single aquarium,
be sure to quarantine all new crayfish specimens for at least a month
before adding it to the main aquarium. That said, realize that crayfish
diseases are often difficult to recognize and even more difficult to
treat.

A final and very important comment!

Do not ever release any crayfish
maintained in captivity into the wild. Also make sure that there is no
possible way for the crayfish to escape into the wild; this is
particularly an issue when keeping crayfish in ponds or outdoor fish
houses.
Crayfish can disrupt entire ecosystems if they are introduced into areas
where they are not native, as has been the case in many parts of the US
and UK. Some US States have begun imposing regulations on the transport
of crayfish for this reason, and in other parts of the world there may
be restrictions on what crayfish can be legally sold as pets. Even if
you think that a particular crayfish is native to your area, there is
still the risk of introducing diseases into the wild crayfish
population.

Many crayfish are only found in specific microhabitats within larger
bodies of water. So even if they are native to your general area, you
may be placing them in inappropriate waterway in that area. Furthermore,
while there are many crayfish species with very wide distributions in a
general sense, in terms of genetics and morphology there may be very
distinct populations of crayfish within certain areas. It’s likely some
of these populations may end up being recognized as distinct races,
subspecies or even new species, so let’s make sure the genetics of
different populations stay in their natural state so that researchers
can get this issue straitened out!

Crayfish can make fascinating pets, but please be
responsible and ensure that your crayfish stays contained. Any unwanted
crayfish should be humanely euthanized or given to a responsible person
who understands this issue and will house or destroy the crayfish as
required.